president obama and the first lady will go to south africa next week and pay their respects. at least two former presidents, bill clinton and george w. bush will also be flying on board air force one. today we spoke with the reverend cecil williams in san francisco about the impact nelson mandela had on his life. >> i was just so overcome by this man who was not just soft- spoken but who articulated and interpreted to people his genuine humanness, his genuine concern for human kind. no wonder he was a world leader. >> this is a photo of reverend williams with nelson mandela. it was taken when the two met in oakland in 1990, just four months after mandela was released from a south african prison where he had been held for 27 years. president obama has ordered all flags on federal buildings to be flown at half staff in honor of nelson man dell la. the flag was also lowered today at the state capitol, one of the wayscalifornians are paying tribute. san francisco will host a civic memorial mall to remember the -- memorial to remember the life and legacy of the human rights leader